A fuel cell is a device which can readily convert chemical energy into electrical and heat energy by the reaction of a fuel gas with a suitable oxidant supply. In a proton exchange membrane fuel cell, for example, the fuel gas is typically hydrogen and the oxidant supply comprises oxygen (or more typically ambient air). In fuel cells of this type, a membrane electrode diffusion layer assembly is provided and which includes a solid polymer electrolyte which has opposite anode and cathode sides. During operation, fuel gas reacts in the presence of a catalyst which is incorporated into the electrode on the anode side to produce hydrogen ions which migrate through the solid polymer electrolyte to the opposite cathode side. Meanwhile, the oxidant supply introduced to the cathode side is present to react with hydrogen ions in the presence of the catalyst which is incorporated into the electrode, on that side, to produce water and a resulting electrical output.
Many fuel cell designs have been provided through the years, and much research and development activity has been conducted to develop a fuel cell which meets perceived performance and cost per watt requirements for various users. Despite decades of research, fuel cells have not been widely embraced except for narrow commercial applications. While many designs have been proposed and have operated with various degrees of success, shortcomings in some peculiar aspect of their individual designs have resulted in difficulties which have detracted from their widespread commercial acceptance and perceived usefulness.
For example, one of the perceived challenges for fuel cell engineers has been to design fuel cells which can be scaled to size to meet various commercial applications. Still further, efforts have been made, as of late, to design fuel cells which can be readily maintained by providing a modular design which allows a failing module to be removed from service while the remaining modules continue operating. Modular fuel cell construction is disclosed in further detail in the following U.S. Patents, all of which are incorporated by reference herein: U.S. Pat. Nos. 6,030,718; 6,096,449; 6,218,035; 6,387,556; 6,467,334; 6,468,682; 6,497,974; and co-pending U.S. patent application Ser. No. 10/033,599 now U.S. Pat. No. 6,716,549 and 10/289,694.
In several of the references noted above, the inventors have addressed some of the remaining challenges in fuel cell construction including the reduction of contact resistance in the fuel cell in order to increase electrical output. Still further, various gas diffusion layers and other constructions are disclosed and which optimize the relative hydration of the ion exchange membrane and extend the operational temperature range of the fuel cell.
An air cooled fuel cell module which addresses the perceived shortcomings in the prior art teachings and practices is the subject matter of the present application.